Time around a lot of working breeds: German Shepherds, Belgian Malinois, Dutch Shepherds, etc. I've been bit once by a German Shepherd....and that was partially my fault.
My pits were the sweetest dogs ever. Never had a single moments problem. My pits were babies. They were scared of cats and were socialized with other dogs from a very young age so they never had aggression issues towards other dogs. My stupid Shorkie (Shih Tzu Yorkie) mix has been more aggressive than my pits ever were.